The present invention relates to so-called veneer lathe charging apparatus employed to load a log onto a veneer lathe for peeling. More particularly, the present invention pertains to a charging apparatus including an electro-optical scanning system coupled to a computer for determining an optimum spin axis. Charger arms on the apparatus are selectively adjustable to transfer the log so that its spin axis is aligned in the chucks of the lathe.
Known veneer lathe charging apparatus typically take the form of an upright frame structure having spaced apart charger arms which are pivotally connected at the top of the structure. A log to be peeled is fed into the structure in a direction with its longitudinal axis generally perpendicular to the direction of travel. The log is deposited on yokes or so-called V's. Disposed above the V's are inverted V's. Both sets of V's are interconnected by a mechanism which simultaneously displaces the V's toward each other at an equal rate. Thus, the log is moved to a position whereby an axis approximating its center is maintained between the V's. The V's will always contact the log equidistant from a predetermined axis, which axis becomes the spin axis.
At this point, the charger arms are angularly displaced from a pre-spot position so that the log is gripped at its opposite ends. The V's are then simultaneously retracted, and the charger arms are pivoted toward the veneer lathe. The log is thereby transferred into the lathe in a position wherein the approximate log center or spin axis is aligned within the chucks on the veneer lathe. The chucks are then actuated to grip the log about the spin axis. The log is then rotated and veneer is peeled therefrom.
There are several significant disadvantages with the above-described apparatus. First of all, it can be readily appreciated that because logs do not have a uniformly round profile, the V's simply cannot accurately determine the longitudinal axis or optimum spin axis of a log. Therefore, when the log is transferred to the veneer lathe, and the chucks are extended to grip the log and rotate same, the log will not be rotated about its optimum spin axis. As a result, precession will occur during peeling of veneer, which decreases the usable amount of veneer peeled from the log.
Because of the nation's dwindling timber resources, and because it is economically unfeasible to waste material during veneer peeling, there have been proposals directed to more accurately determining the optimum spin axis of a log. Prior art proposals have defined the optimum spin axis as being the axis of the largest right cylinder found within the volume of a log. In order to accurately located such a spin axis, it has been proposed to determine the surface configuration of a log prior to its peeling into veneer. Once the surface configuration has been determined, it is a simple matter to calculate the sought for right cylinder. Systems have been proposed for determining the surface configuration using light radiation sources for transmitting light to the log's surface and measuring the time for the reflected light to return to a transceiver. The log is rotated and the measurements are taken for different angular displacements through 360.degree.. The surface configuration of a log is thereby determined.
A problem present with the light radiating and reflection system resides in the fact that a log will often have concave surfaces. Thus, when light is directed toward the log it will travel to an innermost portion of a concave surface before it is reflected back to the transceiver. Consequently, if there are plural concave regions, the right cylinder computed will lie inwardly of such regions. Thus, as the log is rotated about the computed spin axis in a veneer lathe (corresponding to the longitudinal axis of the right cylinder), small strips of veneer will be peeled from the log adjacent to the concave portions. Optimum veneer yield will not be obtained.
Additionally, once the optimum spin axis according to the above-described system has been determined, it is also difficult to accurately transfer the log from its scanning position so that the spin axis is accurately aligned with the chucks of a veneer lathe. The spin axis intersects the ends of the log at different points offset from the axis used during scanning.
Accordingly, it is a general object of the present invention to provide a charging apparatus which will accurately determine an optimum spin axis not necessarily defined by the axis of the largest right cylinder included within the volume of a log. To provide such an apparatus, the present invention uses an electro-optical "break beam" scanning system in which the log is rotated through light beams being emitted from sources to detectors. Such a system will not determine the surface configuration of a rotating log based upon interior regions of concave portions of the log. A computer receives data transmitted from the sources and detectors and calculates the optimum log spin axis which may include a cylinder lying partially outside the surface configuration or periphery of the log.
Another object of the present invention is to provide a charging apparatus in which each of the charger arms is operable independently from one another and is adjustable for precisely positioning a predetermined log spin axis in alignment with the chucks of a veneer lathe. Each arm is provided with a log gripping means or shoe which can be selectively extended or retracted to vary the length of the arm from the arm's pivot axis to a point defined by the shoe. Additionally, each arm is pivotally moved by a fluid actuated cylinder, which cylinder is selectively shiftable along the horizontal.
Another object of the present invention is to provide a scanning system in which an extendible-retractable spindle grips and rotates the log during a scanning operation.
These and other objects and attendant advantages of the present invention will be more readily understood from a consideration of the drawings and the detailed description which follow.